Integrated circuit voltage regulator with adaptive current bleeder circuit

Abstract

An integrated circuit with voltage regulator circuitry is provided. The voltage regulator circuitry may include an adaptive bleeder circuit. The adaptive bleeder circuit may include one or more switchable current leaker paths and an associated bleeder control circuit having current sensing circuitry and voltage comparison circuitry. The current sensing circuitry may monitor the amount of current that is being delivered to a load circuit, whereas the voltage comparison circuitry may output control signals that selectively activate one or more of the current leaker paths depending on the monitored current values. Adaptive bleeder circuit configured in this way can help maintain stability of the voltage regulator while minimizing dynamic power consumption.

What is claimed is: 
     
       1. Voltage regulator circuitry, comprising:
 an operational amplifier; 
 a pass transistor coupled to the operational amplifier in a negative feedback configuration; and 
 an adaptive bleeder circuit that is coupled to the pass transistor and that is selectively activated to provide at least one leakage current path for the voltage regulator circuitry, wherein the adaptive bleeder circuit includes current sensing circuitry and voltage comparison circuitry, wherein the current sensing circuitry has an input that is connected to an output of the operational amplifier and has an output that is connected to an input of the voltage comparison circuitry, wherein the input of the voltage comparison circuitry is shorted to an input of the operational amplifier, wherein the pass transistor is used to deliver a load current, and wherein the leakage current path in the adaptive bleeder circuit is activated when the load current falls below a predetermined threshold and is deactivated when the load current exceeds the predetermined threshold. 
 
     
     
       2. The voltage regulator circuitry defined in  claim 1 , wherein the leakage current path includes a resistor and a switch coupled in series with the pass transistor. 
     
     
       3. The voltage regulator circuitry defined in  claim 2 , wherein the adaptive bleeder circuit further includes a control circuit that generates an output signal for controlling the switch. 
     
     
       4. The voltage regulator circuitry defined in  claim 3 , wherein the control circuit in the adaptive bleeder circuit includes the current sensing circuitry and voltage comparison circuitry. 
     
     
       5. The voltage regulator circuitry defined in  claim 4 , wherein the current sensing circuitry comprises current mirroring circuitry. 
     
     
       6. The voltage regulator circuitry defined in  claim 4 , wherein the voltage comparison circuitry comprises a comparator having a first input that receives a sensing voltage from the current sensing circuitry, a second input that is directly coupled to the pass transistor, and an output on which the output signal of the control circuit is provided. 
     
     
       7. The voltage regulator circuitry defined in  claim 4 , wherein the voltage comparison circuitry exhibits hysteresis. 
     
     
       8. A method of operating voltage regulator circuitry, comprising:
 using a pass transistor in the voltage regulator circuitry to deliver a load current at an output node; 
 using an operational amplifier in the voltage regulator circuitry to control the pass transistor; 
 with an adaptive bleeder circuit in the voltage regulator circuitry, selectively activating a bleeder current path at the output node, wherein selectively activating the bleeder current path comprises:
 enabling the bleeder current path in response to determining that the load current falls below a first predetermined threshold level; and 
 disabling the bleeder current path in response to determining that the load current exceeds the first predetermined threshold level; and 
 
 selectively activating an additional bleeder current path at the output node. 
 
     
     
       9. The method defined in  claim 8 , wherein the bleeder current path includes a resistor and a switch, and wherein selectively activating the bleeder current path comprises selectively turning on the switch when a predetermined criterion is met. 
     
     
       10. The method defined in  claim 8 , further comprising:
 with current sensing circuitry in the adaptive bleeder circuit, monitoring an amount of current that flows through the pass transistor to produce a corresponding sensing voltage. 
 
     
     
       11. The method defined in  claim 8 , wherein selectively activating the additional bleeder current path comprises:
 enabling the additional bleeder current path in response to determining that the load current falls below a second predetermined threshold level that is different than the first predetermined threshold level; and 
 disabling the bleeder current path in response to determining that the load current exceeds the second predetermined threshold level. 
 
     
     
       12. The method defined in  claim 10 , further comprising:
 with voltage comparator circuitry in the adaptive bleeder circuit, receiving the sensing voltage from the current sensing circuitry at a first input, receiving a regulated voltage at a second input, and outputting a corresponding control signal that determines whether the bleeder current path is activated. 
 
     
     
       13. Circuitry, comprising:
 first and second power supply lines; 
 a pass transistor having a first source-drain terminal that is coupled to the first power supply line, a gate terminal, and a second source-drain terminal; 
 an operational amplifier having a first input that receives a reference voltage, a second input that receives a regulated voltage from the second source-drain terminal of the pass transistor, and an output that is coupled to the gate terminal of the pass transistor; 
 a current leaker path having a resistive circuit and a switching component directly coupled in series between the second source-drain terminal of the pass transistor and the second power supply line; and 
 an additional current leaker path having another resistive circuit and another switching component coupled in series between the second source-drain terminal of the pass transistor and the second power supply line. 
 
     
     
       14. The circuitry defined in  claim 13 , wherein the switching component in the current leaker path is activated in response to a first criterion being satisfied, and wherein the another switching component in the additional current leaker path is activated in response to a second criterion that is different than the first criterion being satisfied. 
     
     
       15. The circuitry defined in  claim 13 , further comprising:
 current sensing circuitry that monitors how much current is flowing through the pass transistor and that produces first and second current sensing voltage signals. 
 
     
     
       16. The circuitry defined in  claim 15 , further comprising:
 a first comparator having a positive input that receives the regulated voltage, a negative input that receives the first current sensing voltage signal, and an output that is coupled to the switching component in the current leaker path; and 
 a second comparator having a positive input that receives the regulated voltage, a negative input that receives the second current sensing voltage signal, and an output that is coupled to the another switching component in the additional current leaker path.